What is this R doing at the fb loop?

Stompboxes circuits published in magazines, books or on DIY electronics websites.
Post Reply
Enrulado
Information
Posts: 3
Joined: 01 Dec 2007, 23:06
Location: Argentina
Has thanked: 2 times
Contact:

Post by Enrulado »

I know it may be fairly simple, but i'm having some trouble figuring it out ... why is R23 there?
I guess it's a compression thing, but not for sure.

It's the schematic of a SS Fender Amp ... nice cleans but awful (really, disgusting) distortion channel.

Thanks!!!

Image
https://www.dropbox.com/s/s5xzfbsclir1p ... r.jpg?dl=0

heaterman
Information
Posts: 25
Joined: 27 Jul 2017, 08:44
Has thanked: 8 times
Been thanked: 18 times

Post by heaterman »

hey!

Not shure, but i guess R23 is bypassing some signal around D3 and D4, so not all of the signal is going through D3 and D4, which means that they clip less.

Manfred
Transistor Tuner
Information
Posts: 1137
Joined: 04 Apr 2009, 23:42
Has thanked: 1104 times
Been thanked: 712 times

Post by Manfred »

Compared to a common diode, an LED has a significantly higher junction capacitance.
So my guess is that this junction capacitance in series with the 220k resistor will reduce the gain at higher frequencies as long as the LED and diode voltages remain below their threshold voltage.
If I am right, this would be a very tricky circuit design.
FB_Resistor.jpg

Manfred
Transistor Tuner
Information
Posts: 1137
Joined: 04 Apr 2009, 23:42
Has thanked: 1104 times
Been thanked: 712 times

Post by Manfred »

In this essay a diagram is shown with the curve of the capacity as a function of the voltage across the LED:
https://www.edn.com/an-leds-intrinsic-c ... c-circuit/

Post Reply